It is known from European patent application No. 29265 that 3-carboxyazetidine and related compounds are chemical hybridizing agents, their mode of action presumably being based on their ability to produce male sterility in plants. That application also describes a process for their preparation, starting from 3-cyano-1-diphenyl-methylazetidine, which may be prepared by methods known per se. Although the process described works well, it is not ideally suited for large scale preparations, since the bulky diphenylmethyl group on the nitrogen atom is removed only in the last of a series of steps, which means that in all but the last step large equipment is needed. Moreover, the parent starting compound diphenylmethylamine is relatively expensive.
It is the object of the invention therefore to provide an improved process for the preparation of a 3-carboxyazetidine compound, which is achieved firstly by the provision of novel intermediates and secondly by the provision of a process for their preparation, starting from readily available compounds.